Process to make olefins from isobutanol

ABSTRACT

A process for the conversion of an alcohol mixture to make propylene may include introducing into a reactor a stream that includes the alcohol mixture. The alcohol mixture may include 20 to 100 weight percent isobutanol. The process may include contacting the stream with a single catalyst at a temperature above 450° C. in the reactor at conditions effective to dehydrate the isobutanol, forming C 4   +  olefins, and to catalytically crack the C 4   +  olefins. The single catalyst may be an acid catalyst adapted to cause both the dehydration and the catalytic cracking. The process may include recovering from the reactor an effluent that includes ethylene, propylene, water, and various hydrocarbons. The process may include fractionating the effluent to produce an ethylene stream, a propylene stream, a fraction of hydrocarbons having 4 carbon atoms or more, and water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/694,282, filed on Apr. 23, 2015, which is a Continuation of U.S.patent application Ser. No. 13/813,168, filed on Apr. 5, 2013, nowissued as U.S. Pat. No. 9,056,807, which is a National Stage Entry ofPCT/EP2011/061583, filed on Jul. 8, 2011, which claims priority from EP10171672.8, filed on Aug. 3, 2010.

FIELD OF THE INVENTION

The present invention relates to the simultaneous dehydration andcracking of isobutanol on a catalyst to produce an olefin streamcomprising propylene. The limited supply and increasing cost of crudeoil has prompted the search for alternative processes for producinghydrocarbon products such as propylene. i-Butanol can be obtained byfermentation of carbohydrates coming from the biomass, via the syngasroute or base-catalysed Guerbet condensation. Made up of organic matterfrom living organisms, biomass is the world's leading renewable energysource.

BACKGROUND OF THE INVENTION

The bio-ethanol is one of the most relevant sources of bio-carbon today.This platform molecule available today at a price of its calorific valueis venturing out of fuel application being used as precursor for basechemicals. While the ethylene can easily produced by dehydration fromethanol, the direct conversion of ethanol to propylene is problematicdue to very low yield.

One step process provides a wide diversity in the formed productsobtained in minor amounts which monetizing is not very obvious.Multistep process which includes ethanol dehydration to ethylene, offersbetter overall selectivity to propylene. However, the obtained ethylenehas to be first dimerized to butene or oligomerized to be furtherreacted via metathesis or via cracking in OCP (olefin cracking process)reactor. The complexity of the multistep process increases significantlythe manufacturing costs of bio-propylene.

The way to produce bio-propylene can be accomplished by employing a newconcept: using isobutanol as a platform molecule. Of the describedroutes towards isobutanol, the Guerbet condensation, the synthesis gasconversion to alcohols and the 2-keto acid pathway from carbohydratesare routes that can use biomass as primary feedstock. The fermentationof sugar as well as a syngas conversion may result directly to formationof heavy alcohols (C3+), in particular i-butanol, which is often anabundant product (Applied Catalysis A, general, 186, p. 407, 1999 andChemiker Zeitung, 106, p. 249, 1982).

Gasification of biomass results in synthesis gas that can be convertedafter purification into methanol, ethanol, propanol or directly intoisobutanol. In addition, methanol and ethanol or propanol resourced frombiomass can be further condensed to isobutanol. The base-catalysedGuerbet condensation of methanol with ethanol and/or propanol increasesthe concentration of i-butanol in the alcohol fraction and in particularin C3+ heavy alcohols fraction (J. of Molecular Catalysis A: Chemical200, 137, 2003 and Applied Biochemistry and Biotechnology, 113-116, p.913, 2004).

Isobutanol (2-methyl-1-propanol) has historically found limitedapplications and its use resembles that of 1-butanol. It has been usedas solvent, diluent, wetting agent, cleaner additive and as additive forinks and polymers. Recently, isobutanol has gained interest as fuel orfuel component as it exhibits a high octane number (Blend Octane R+M/2is 102-103) and a low vapor pressure (RVP is 3.8-5.2 psi).

Isobutanol is often considered as a byproduct of the industrialproduction of 1-butanol (Ullmann's encyclopedia of industrial chemistry,6^(th) edition, 2002). It is produced from propylene viahydroformylation in the oxo-process (Rh-based catalyst) or viacarbonylation in the Reppe-process (Co-based catalyst). Hydroformylationor carbonylation makes n-butanal and iso-butanal in ratios going from92/8 to 75/25. To obtain isobutanol, the iso-butanal is hydrogenatedover a metal catalyst.

Recently, new biochemical routes have been developed to produceselectively isobutanol from carbohydrates. The new strategy uses thehighly active amino acid biosynthetic pathway of microorganisms anddiverts its 2-keto acid intermediates for alcohol synthesis. 2-Ketoacids are intermediates in amino acid biosynthesis pathways. Thesemetabolites can be converted to aldehydes by 2-keto-acid decarboxylases(KDCs) and then to alcohols by alcohol dehydrogenases (ADHs). Twonon-native steps are required to produce alcohols by shuntingintermediates from amino acid biosynthesis pathways to alcoholproduction (Nature, 451, p. 86, 2008 and US patent 2008/0261230).Recombinant microorganisms are required to enhance the flux of carbontowards the synthesis of 2-keto-acids. In the valine biosynthesis2-ketoisovalerate is an intermediate. Glycolyse of carbohydrates resultsin pyruvate that is converted into acetolactate by acetolactatesynthase. 2,4-dihydroxyisovalerate is formed out of acetolactate,catalysed by isomeroreductase. A dehydratase converts the2,4-dihydroxyisovalerate into 2-keto-isovalerate. In the next step, aketo acid decarboxylase makes isobutyraldehyde from 2-keto-isovalerate.The last step is the hydrogenation of isobutyraldehyde by adehydrogenase into isobutanol.

The direct 2-keto acid pathway can produce isobutanol from carbohydratesthat are isolated from biomass. Simple carbohydrates can be obtainedfrom plants like sugar cane, sugar beet. More complex carbohydrates canbe obtained from plants like maize, wheat and other grain bearingplants. Even more complex carbohydrates can be isolated fromsubstantially any biomass, through unlocking of cellulose andhemicellulose from lignocelluloses.

The isobutanol can be dehydrated to corresponding mixture of olefinscontaining the same number of atoms. Dehydration of butanols has beendescribed on alumina-type catalysts (Applied Catalysis A, General, 214,p. 251-257, 2001). Both double-bond shift and skeletal isomerisation hasbeen obtained at very low space velocity (or very long reaction time)corresponding to a GHSV (Gas Hourly Space Velocity=ratio of feed rate(gram/h) to weight of catalyst (ml)) of less than 1 gram·ml⁻¹·h⁻¹. Thedehydration reactions of alcohols to produce alkenes with the samenumber of carbons have been known for a long time (J. Catal. 7, p. 163,1967 and J. Am. Chem. Soc. 83, p. 2847, 1961). Many available solid acidcatalysts can be used for alcohol dehydration (Stud. Surf. Sci. Catal.51, p. 260, 1989), the European patent EP0150832, Bulletin of theChemical Society of Japan, vol 47(2), 424-429 (1974). However,γ-aluminas are the most commonly used, especially for the longer chainalcohols (with three and more carbon atoms). This is because catalystswith stronger acidity, such as the silica-aluminas, molecular sieves,zeolites or resin catalysts can promote double-bond shift, skeletalisomerization and other olefin interconversion reactions.

The primary product of the acid-catalysed dehydration of isobutanol isiso-butene and water:

So, the dehydration may result in substantially pure isobutene stream orin blended olefinic stream reach in butenes if a secondary reactionoccurs on the catalyst.

The production of light olefins (ethylene and propylene) from a mixedalcohol feedstock in an oxygenates to olefins process has been describedin the U.S. Pat. No. 7,288,689. Said patent provides various processesfor producing C1 to C4 alcohols, optionally in a mixed alcohol stream,and optionally converting the alcohols to light olefins. In oneembodiment, it includes directing a first portion of a syngas stream toa methanol synthesis zone wherein methanol is synthesized. A secondportion of the syngas stream is directed to a fuel alcohol synthesiszone wherein fuel alcohol is synthesized. The methanol and at least aportion of the fuel alcohol are directed to an oxygenate to olefinreaction system for conversion thereof to ethylene and propylene. Inthis prior art “fuel alcohol” means an alcohol-containing compositioncomprising ethanol, one or more C3 alcohols, one or more C4 alcohols andoptionally one or more C5+ alcohols. At col 21 lines 14+ is mentioned “. . . Additionally or alternatively, the fuel alcohol-containing streamcomprises one or more C4 alcohols, preferably on the order of from about0.1 to about 20 weight percent C4 alcohols, preferably from about 1 toabout 10 weight percent C4 alcohols, and most preferably from about 2 toabout 5 weight percent C4 alcohols, based on the total weight of thefuel alcohol-containing stream. The fuel alcohol-containing streampreferably comprises at least about 5 weight percent C3-C4 alcohols,more preferably at least about 10 weight percent C3-C4 alcohols, andmost preferably at least about 15 weight percent C3-C4 alcohols . . . ”.Preferably, the molecular sieve catalyst composition comprises a smallpore zeolite or a molecular sieve selected from the group consisting of:MeAPSO, SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20,SAPO-031, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42,SAPO-44, SAPO-47, SAPO-56, AEI/CHA intergrowths, metal containing formsthereof, intergrown forms thereof, and mixtures thereof.

EP 2070896 A1 describes the dehydration of 1-butanol on a porouscrystalline aluminosilicate (TON type) in the hydrogen form. At 500° C.the products are in wt %:

propylene 10.76

trans-butene-2 16.99

butene-1 13.49

isobutene 31.30

cis-butene-2 13.33

U.S. Pat. No. 6,768,037 describes a process for upgrading aFischer-Tropsch product comprising paraffins, oxygenates (alcohols), andC6+ olefins. The process includes contacting the Fischer-Tropsch productwith an acidic olefin cracking catalyst (ZSM-5) to convert theoxygenates and C6+ olefins to form light olefins. The contactingconditions include a temperature in the range of about 500° F. to 850°F., a pressure below 1000 psig, and a liquid hourly space velocity inthe range of from about 1 to 20 hr⁻¹. The process further includesrecovering the Fischer-Tropsch product comprising unreacted paraffins,and recovering the light olefins. At col 6 lines 16+ is mentioned “ . .. The product from a Fischer-Tropsch process contains predominantlyparaffins; however, it may also contain C₆₊ olefins, oxygenates, andheteroatom impurities. The most abundant oxygenates in Fischer-Tropschproducts are alcohols, and mostly primary linear alcohols. Less abundanttypes of oxygenates in Fischer-Tropsch products include other alcoholtypes such as secondary alcohols, acids, esters, aldehydes, and ketones. . . ”.

U.S. Pat. No. 4,698,452 relates to a novel process for the conversion ofethanol or its mixtures with light alcohols and optionally water intohydrocarbons with specific and unusual selectivity towards ethylene.More particularly, it relates to the use of ZSM-5 zeolite basedcatalysts into which Zn alone or Zn and Mn are incorporated. Thepreferred reaction conditions used in the experiments are as follows:temperature=300° C.-450° C. (most preferred 400° C.); catalyst weight=4g; total pressure=1 atm; alcohol or aqueous ethanol pressure=0.9 atm;inert gas (stripping gas)=nitrogen; weight hourly space velocity(W.H.S.V.)=2.4 h-1; duration of a run=4 hours. At table 3 dehydration ofisobutanol has been made on ZSM-5 (Zn—Mn) and produces paraffins C1-C4,ethylene, propylene, butenes, aromatics and aliphatics.

It has now been discovered that isobutanol or a mixture of isobutanoland other alcohols containing two and more carbon atoms can besimultaneously dehydrated and cracked to propylene in a one-pot reactorto produce propylene rich feedstock over hydrothermally stable catalyst.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a process for the conversion of analcohol mixture (A) comprising about 20 w % to 100% isobutanol to makeessentially propylene, comprising:

a) introducing in a reactor (A) a stream comprising the mixture (A),optionally water, optionally an inert component,

b) contacting said stream with a catalyst (A1) at a temperature above450° C. in said reactor (A) at conditions effective to dehydrate atleast a part of the isobutanol and other alcohols, if any, and make acracking,

c) recovering from said reactor (A) an effluent comprising: ethylene,propylene, water, optionally unconverted alcohols of the mixture (A),various hydrocarbons, and the optional inert component of step a),

d) fractionating said effluent of step c) to produce at least anethylene stream, a propylene stream, a fraction consisting essentiallyof hydrocarbons having 4 carbon atoms or more, water and the optionalinert component of step a),

optionally recycling ethylene in whole or in part at the inlet of thereactor (A), optionally recycling the fraction consisting essentially ofhydrocarbons having 4 carbon atoms or more at the inlet of the reactor(A).

Advantageously, before recycling said hydrocarbons having 4 carbon atomsor more at the inlet of the reactor (A), said hydrocarbons having 4carbon atoms or more are sent to a second fractionator to purge theheavies, water and optionally oxygenates.

In an embodiment the alcohol feed is subjected to purification to reducethe content in the metal ions, in more particularly in Na, Fe, K, Ca andAl.

In a specific embodiment the alcohol mixture (A) comprises 40 to 100 w %of isobutanol.

In a specific embodiment the alcohol mixture (A) comprises 60 to 100 w %of isobutanol.

In a specific embodiment the alcohol mixture (A) comprises 80 to 100 w %of isobutanol.

In a specific embodiment the alcohol mixture (A) comprises essentiallyisobutanol.

Optionally, the alcohol mixture (A) can be fed to the catalyst inpresence of steam (at least 10 wt % of i-Butanol).

i-Butanol may have fossil origin, but in preferred embodiment at least apart of used feedstock is derived from biomass.

Advantageously, the alcohols of the mixture (A) are derived from thebiomass and thus it gives the opportunities to introduce a part ofrenewable carbon in the light olefin product.

Advantageously isobutanol is obtained by fermentation of carbohydratescoming from the biomass, or from the syngas route or from thebase-catalysed Guerbet condensation.

In an embodiment isobutanol is produced by the direct 2-keto acidpathway from carbohydrates that are isolated from biomass.

One skilled in the art will also appreciate that the olefin productsmade by the present invention can be polymerized, optionally withcomonomers, to form polyolefins, particularly polyethylenes andpolypropylenes.

DETAILED DESCRIPTION OF THE INVENTION

As regards the stream introduced at step a), and the alcohols in themixture (A) besides isobutanol, one can cite ethanol, propanol,isopropanol, 1-butanol and 2-butanol and the higher alcohols.

the inert component is any component provided there is no adverse effecton the catalyst. Because the dehydration is endothermic the inertcomponent can be used to bring energy. By way of examples the inertcomponent is selected among the saturated hydrocarbons having up to 10carbon atoms, naphtenes, nitrogen and CO₂. An example of inert componentcan be any individual saturated compound, a synthetic mixture of theindividual saturated compounds as well as some equilibrated refinerystreams like straight naphtha, butanes etc. Advantageously it is asaturated hydrocarbon or a mixture of saturated hydrocarbons having from3 to 7 carbon atoms, more advantageously having from 4 to 6 carbon atomsand is preferably pentane. The weight proportions of respectivelyalcohols, water and inert component are, for example, 5-100/0-95/0-95(the total being 100). The stream comprising the alcohol mixture (A) canbe liquid or gaseous.

The isobutanol-containing feed can be produced by the Guerbetcondensation, the synthesis gas route and the biochemical routes. Thefeedstock before feeding to cracking reactor can be subjected to adifferent upgrading procedure including but non-limiting to purificationfrom the metals, separation/extractions of the individual compounds,alcohols interconversion, partial dehydration to ethers, drying etc. Thefeedstock is essentially free of light alcohols and hydrocarbons. Theweight content of these compounds in the mixture is below 10 wt %.

As regards the reactor (A), it can be a fixed bed reactor, a moving bedreactor or a fluidized bed reactor. A typical fluid bed reactor is oneof the FCC type used for fluidized-bed catalytic cracking in the oilrefinery. A typical moving bed reactor is of the continuous catalyticreforming type. The dehydration/cracking may be performed continuouslyin a fixed bed reactor configuration using a pair of parallel “swing”reactors. The various preferred catalysts of the present invention havebeen found to exhibit high stability. This enables thedehydration/cracking process to be performed continuously in twoparallel “swing” reactors wherein when one reactor is operating, theother reactor is undergoing catalyst regeneration. The catalyst of thepresent invention also can be regenerated several times.

As regards the catalyst (A1) of step b), it can be any acid catalystcapable to cause the simultaneous dehydration and cracking of alcoholsunder above said conditions. By way of example it can be; zeolites,P-zeolites, Me-zeolites, alumina, silica-alumina, clays.

The catalyst is employed under particular reaction conditions whereby,further to the dehydration of isobutanol, the catalytic cracking of theC₄ ⁺ olefins readily proceeds. Different reaction pathways can occur onthe catalyst. Olefinic catalytic cracking may be understood to comprisea process yielding shorter molecules via bond breakage.

The process conditions are selected in order to provide high selectivitytowards propylene or ethylene, as desired, a stable olefin conversionover time, and a stable olefinic product distribution in the effluent.Such objectives are favoured with a low pressure, a high inlettemperature and a short contact time, all of which process parametersare interrelated and provide an overall cumulative effect. The processconditions are selected to disfavour hydrogen transfer reactions leadingto the formation of paraffin's, aromatics and coke precursors.

According to an embodiment the catalyst (A1) is a crystalline PorousAluminophosphate containing advantageously at least one 10 and/or 12members ring into the structure.

The porous crystalline aluminophosphate may be one that is comprised ofaluminum and phosphorus that are partly substituted by silicon, boron,Ni, Zn, Mg, Mn such as a porous crystalline metalaluminophosphate. Thestructure of such crystalline porous aluminophosphates may, for example,be those that are identified by codes for zeolites described above asAEL, AFI, AFO or FAU.

The above porous crystalline aluminophosphate is preferably a porouscrystalline silicoaluminophosphate. Specifically, SAPO5, and the likehaving an AFI structure, SAPO41, and the like having an AFO structure,SAPO11, and the like having an AEL structure, structure or SAPO37, andthe like having a FAU structure may be mentioned.

In an embodiment, the small pore molecular sieves can be selected fromthe group of CHA (SAPO 34, 44), AEI (SAPO 18), LEV (SAPO 35), ERI (SAPO17) or a mixture of thereof including intergrowth phases.

According to another specific embodiment, suitable catalysts for thepresent process is the silicoaluminophosphate molecular sieves, inparticular of the AEL group with typical example the SAPO-11 molecularsieve. The SAPO-11 molecular sieve is based on the ALPO-11, havingessentially an Al/P ratio of 1 atom/atom. During the synthesis siliconprecursor is added and insertion of silicon in the ALPO frameworkresults in an acid site at the surface of the micropores of the10-membered ring sieve. The silicon content ranges from 0.1 to 10 atom %(Al+P+Si is 100).

Various commercial zeolite products nay be used, or it is possible touse zeolites that have been synthesized by a known method disclosed ine.g. “Verified Synthesis of Zeolitic Materials” (2^(nd) Revised Edition2001 Elsevier) published by the above IZA.

According to an embodiment the catalyst (A1) is a crystalline silicatecontaining advantageously at least one 10 members ring into thestructure. It is by way of example of the MFI (ZSM-5, silicalite-1,boralite C, TS-1), MEL (ZSM-11, silicalite-2, boralite D, TS-2, SSZ-46),FER (Ferrierite, FU-9, ZSM-35), MTT (ZSM-23), MWW (MCM-22, PSH-3, ITQ-1,MCM-49), TON (ZSM-22, Theta-1, NU 10), EUO (ZSM-50, EU-1), MFS (ZSM-57),CON (CIT-1) and ZSM-48 family of microporous materials consisting ofsilicon, aluminium, oxygen and optionally boron. Advantageously in saidfirst embodiment the catalyst (A1) is a crystalline silicate, metalcontaining crystalline silicate or a dealuminated crystalline silicate.

The crystalline silicate can have a ratio Si/Al of at least about 100and is advantageously selected among the MFI and the MEL and modifiedwith the metals Mg, Ca, La, Ni, Ce, Zn, Co, Ag, Fe, Cu. The metalcontent is at least 0.1 wt %.

The dealuminated crystalline silicate is advantageously such as about10% by weight of the aluminium is removed. Such dealumination isadvantageously made by a steaming optionally followed by a leaching.

In another specific embodiment the crystalline silicate catalyst ismixed with a binder, preferably an inorganic binder, and shaped to adesired shape, e.g. pellets. The binder is selected so as to beresistant to the temperature and other conditions employed in thedehydration/cracking process of the invention. The binder is aninorganic material selected from clays, silica, metal silicate, metalborates, metal oxides such as ZrO₂ and/or metals, or gels includingmixtures of silica and metal oxides.

According to an embodiment the catalyst (A1) is a P-modified zeolite(Phosphorus-modified zeolite). Said phosphorus modified molecular sievescan be prepared based on MFI, MOR, MEL, clinoptilolite or FER, MWW, TON,EUO, MFS and ZSM-48 family of microporous molecular sieves having aninitial Si/Al ratio advantageously between 4 and 500. The P-modifiedzeolites of this recipe can be obtained based on cheap crystallinesilicates with low Si/Al ratio (below 30).

By way of example said P-modified zeolite is made by a processcomprising in that order:

-   -   selecting a zeolite (advantageously with Si/Al ratio between 4        and 500) among H⁺ or NH₄ ⁺-form of MFI, MEL, FER, MOR,        clinoptilolite, MWW, TON, EUO, MFS and ZSM-48;    -   introducing P at conditions effective to introduce        advantageously at least 0.05 wt % of P;    -   separation of the solid from the liquid if any;    -   an optional washing step or an optional drying step or an        optional drying step followed by a washing step;    -   a calcination step.

The zeolite with low Si/Al ratio has been made previously with orwithout direct addition of an organic template.

Optionally the process to make said P-modified zeolite comprises thesteps of steaming and leaching. The method consists in steaming followedby leaching. It is generally known by the persons in the art that steamtreatment of zeolites, results in aluminium that leaves the zeoliteframework and resides as aluminiumoxides in and outside the pores of thezeolite. This transformation is known as dealumination of zeolites andthis term will be used throughout the text. The treatment of the steamedzeolite with an acid solution results in dissolution of theextra-framework aluminiumoxides. This transformation is known asleaching and this term will be used throughout the text. Then thezeolite is separated, advantageously by filtration, and optionallywashed. A drying step can be envisaged between filtering and washingsteps. The solution after the washing can be either separated, by way ofexample, by filtering from the solid or evaporated.

P can be introduced by any means or, by way of example, according to therecipe described in U.S. Pat. No. 3,911,041, U.S. Pat. No. 5,573,990 andU.S. Pat. No. 6,797,851.

The catalyst made of a P-modified zeolite can be the P-modified zeoliteitself or it can be the P-modified zeolite formulated into a catalyst bycombining with other materials that provide additional hardness orcatalytic activity to the finished catalyst product. Advantageously, atleast a part of phosphorous is introduced into zeolite before shaping.In a specific embodiment, the formed P-precursor can be further modifiedwith the metals selected from Mg, Ca, La, Ni, Ce, Zn, Co, Ag, Fe, Cuaccording to the recipe described in WO 09092779 and WO 09092781.

The separation of the liquid from the solid is advantageously made byfiltering at a temperature between 0-90° C., centrifugation at atemperature between 0-90° C., evaporation or equivalent.

Optionally, the zeolite can be dried after separation before washing.Advantageously said drying is made at a temperature between 40-600° C.,advantageously for 1-10 h. This drying can be processed either in astatic condition or in a gas flow. Air, nitrogen or any inert gases canbe used.

The washing step can be performed either during the filtering(separation step) with a portion of cold (<40° C.) or hot water (>40 but<90° C.) or the solid can be subjected to a water solution (1 kg ofsolid/4 liters water solution) and treated under reflux conditions for0.5-10 h followed by evaporation or filtering.

Final equilibration step is performed advantageously at the temperature400-800° C. either in a static condition or in a gas flow. Air, nitrogenor any inert gases can be used.

According to a specific embodiment the phosphorous modified zeolite ismade by a process comprising in that order

-   -   selecting a zeolite (advantageously with Si/Al ratio between 4        and 500, from 4 to 30 in a specific embodiment) among H⁺ or NH₄        ⁺-form of MFI, MEL, FER, MOR, clinoptilolite, MWW, TON, EUO, MFS        and ZSM-48;    -   steaming at a temperature ranging from 400 to 870° C. for        0.01-200 h;    -   leaching with an aqueous acid solution at conditions effective        to remove a substantial part of Al from the zeolite;    -   introducing P with an aqueous solution containing the source of        P at conditions effective to introduce advantageously at least        0.05 wt % of P;    -   separation of the solid from the liquid;    -   an optional washing step or an optional drying step or an        optional drying step followed by a washing step;    -   a calcination step.

Optionally between the steaming step and the leaching step there is anintermediate step such as, by way of example, contact with silica powderand drying.

Optionally the leaching and introducing P are made simultaneously byusing an acid based comprising phosphorus to make the leaching.

Advantageously the selected MFI, MEL, FER, MOR, clinoptilolite, MWW,TON, EUO, MFS and ZSM-48 (or H⁺ or NH₄ ⁺-form MFI, MEL, FER, MOR,clinoptilolite, MWW, TON, EUO, MFS and ZSM-48) has an initial atomicratio Si/Al of 100 or lower and from 4 to 30 in a specific embodiment.The conversion to the H⁺ or NH₄ ⁺-form is known per se and is describedin U.S. Pat. No. 3,911,041 and U.S. Pat. No. 5,573,990.

Advantageously the final P-content is at least 0.05 wt % and preferablybetween 0.3 and 7 w %. Advantageously at least 10% of Al, in respect toparent zeolite MFI, MEL, FER, MOR and clinoptilolite, MWW, TON, EUO, MFSand ZSM-48, have been extracted and removed from the zeolite by theleaching.

Then the zeolite either is separated from the washing solution or isdried without separation from the washing solution. Said separation isadvantageously made by filtration. Then the zeolite is calcined, by wayof example, at 400° C. for 2-10 hours.

In the steam treatment step, the temperature is preferably from 420 to870° C., more preferably from 480 to 760° C. The pressure is preferablyatmospheric pressure and the water partial pressure may range from 13 to100 kPa. The steam atmosphere preferably contains from 5 to 100 vol %steam with from 0 to 95 vol % of an inert gas, preferably nitrogen. Thesteam treatment is preferably carried out for a period of from 0.01 to200 hours, advantageously from 0.05 to 200 hours, more preferably from0.05 to 50 hours. The steam treatment tends to reduce the amount oftetrahedral aluminium in the crystalline silicate framework by formingalumina.

The leaching can be made with an organic acid such as citric acid,formic acid, oxalic acid, tartaric acid, malonic acid, succinic acid,glutaric acid, adipic acid, maleic acid, phthalic acid, isophthalicacid, fumaric acid, nitrilotriacetic acid,hydroxyethylenediaminetriacetic acid, ethylenediaminetetracetic acid,trichloroacetic acid trifluoroacetic acid or a salt of such an acid(e.g. the sodium salt) or a mixture of two or more of such acids orsalts. The other inorganic acids may comprise an inorganic acid such asnitric acid, hydrochloric acid, methansulfuric acid, phosphoric acid,phosphonic acid, sulfuric acid or a salt of such an acid (e.g. thesodium or ammonium salts) or a mixture of two or more of such acids orsalts.

The residual P-content is adjusted by P-concentration in the aqueousacid solution containing the source of P, drying conditions and awashing procedure if any. A drying step can be envisaged betweenfiltering and washing steps.

Said P-modified zeolite can be used as itself as a catalyst. In anotherembodiment it can be formulated into a catalyst by combining with othermaterials that provide additional hardness or catalytic activity to thefinished catalyst product. Materials which can be blended with theP-modified zeolite can be various inert or catalytically activematerials, or various binder materials. These materials includecompositions such as kaolin and other clays, various forms of rare earthmetals, phosphates, alumina or alumina sol, titania, zirconia, quartz,silica or silica sol, and mixtures thereof. These components areeffective in densifying the catalyst and increasing the strength of theformulated catalyst. The catalyst may be formulated into pellets,spheres, extruded into other shapes, or formed into a spray-driedparticles. The amount of P-modified zeolite which is contained in thefinal catalyst product ranges from 10 to 90 weight percent of the totalcatalyst, preferably 20 to 70 weight percent of the total catalyst.

The catalyst (A1) which are not P-modified zeolites can be formulatedwith a binder as explained above for the P-modified zeolites.

The other catalyst components of the catalyst (A1) could be binders,fillers or other catalytically active materials. Clays, modified clays,basic compounds, transition metal-containing compounds as well as smallpore-zeolites and silicoaluminophosphates may be implemented as othercatalytically active materials.

A catalyst has already been described in WO2009098262.

As regards the pressure in steps a) and b), the use of a low alcoholpartial pressure which leads to a low olefin partial pressure, forexample atmospheric pressure, tends to lower the incidence of hydrogentransfer reactions in the cracking process, which in turn reduces thepotential for coke formation which tends to reduce catalyst stability.The partial pressure of the alcohols is advantageously lower than 4 barsabsolute (0.4 MPa) and more advantageously from 0.5 to 4 bars absolute(0.05 MPa to 0.4 MPa), preferably lower than 3.5 bars absolute (0.35MPa) and more preferably lower than 2 bars absolute (0.2 MPa). Thepressure of the reactor of step b) can be any pressure but it is moreeconomical to operate at moderate pressure. By way of example thepressure of the reactor ranges from 1 to 30 bars absolute (0.1 MPa to 3MPa), advantageously from 1 to 20 bars absolute (0.1 MPa to 2 MPa).

As regards the temperature in step b), the reaction is preferablyperformed at an inlet temperature of the feedstock of from 450° to 650°C., more preferably from 500° to 650° C., more preferably from 520° to600° C., yet more preferably from 540° C. to 590° C.

As regards the WHSV of alcohols in step b), it ranges advantageouslyfrom 0.1 to 50 h-1, more advantageously from 1 to 20 h-1, preferablyfrom 5 to 20 h-1, and more preferably from 5 to 15 h-1.

In order to maximize the amount of ethylene and propylene and tominimize the production of methane, aromatics and coke, it is desired tominimize the presence of diolefins in the feed. Diolefin conversion tomonoolefin hydrocarbons may be accomplished with a conventionalselective hydrogenation process such as disclosed in U.S. Pat. No.4,695,560 hereby incorporated by reference.

As regards step d), the fractionation of said effluent of step c) saidfractionation is carried out by any means, they are known per se.

In an embodiment the present invention comprises a further step whereinethylene is reacted with 2-butene from the fraction consistingessentially of hydrocarbons having 4 carbon atoms or more recovered atstep d). Said reaction known as methathesis produces propylene.

As regards the preparation of the metathesis feedstock, it is preferredto remove the iso-butene before metathesis. This can be done by aselective chemical transformation of iso-butene or by distillation.Selective chemical transformations are: (i) oligomerisation, (ii)etherification or (iii) hydration or combinations of them. The resultingproducts are respectively: (i) iso-octenes for use in gasoline, tri,tetra or pentamers of substantially iso-butene for use in Jet fuel orkerozine; (ii) methyl-t-butylether or ethyl-t-butylether; (iii)t-butanol. The oligomers are eventually hydrogenated to thecorresponding paraffin's. The t-butanol can eventually be recycled backinto the reactor (A).

A preferred distillation method is the catalytic distillation duringwhich the 1-butene is continuously transformed into 2-butenes so as tooptimise the 2-butenes yield and minimise entrainment of 1-butene withthe overhead iso-butene. The iso-butene rich overhead can be recyclingback to the reactor (A).

As regards the metathesis catalyst, three types of metal containingcatalysts can be suitable to perform the disproportionation reaction.The co-metathesis reaction of the ethylene with the butene-2 or theautometathesis of a mixture of 1-butene and 2-butene can be catalyzed bythree metallic oxides that are dispersed on carriers: by molybdenum(eventually in combination with cobalt and rhenium), tungsten or rheniumoxides.

A first kind of catalyst is Rhenium supported on alumina-containingcarrier. The Rhenium content can be from 0.5 to 15 wt %.

The metathesis reaction, by way of example, over rhenium heptoxidecatalysts is carried out preferably in a liquid phase, in absence ofoxygen-containing compounds and moisture, and at a temperature of 0 to150° C., preferably 20 to 100° C., under a pressure at least to keep thereaction mixture at the reaction temperature in the liquid state.

A second type of catalyst is tungsten supported on silica carrier. Thetungsten content can be from 1 to 15 wt %. The tungsten based catalystsare advantageously used in combination with a co-catalyst. Lithium,sodium, potassium, cesium, magnesium, calcium, strontium, barium, zinc,lanthanum and yttrium are preferred.

A third type of catalyst is molybdenum supported on alumina or silicacarrier. Suitable molybdenum oxide based catalysts are disclosed in U.S.Pat. No. 3,658,927 and U.S. Pat. No. 4,568,788.

The activity of the metathesis catalyst is generally decreased by polarcompounds like moisture, carbon dioxide, carbon monoxide, dienecompounds, sulphur and nitrogen compounds, alcohols, aldehydes andcarboxylic compounds. Accordingly, the olefins used as feedstockpreferably should be purified from impurities. Such impurities areremoved by distillation, adsorption, extraction or washing. Othermaterials used during the process like nitrogen gas and hydrogen gasthat are introduced into the reactor need also extensive purification.Nitrogen is often needed to purge reactors from moisture, reducingagents (carbon monoxide, ethylene or hydrogen) and resulting residuesfrom this reduction.

Furthermore, the activity of the metathesis catalyst can further beincreased or stabilised by in the presence of hydrogen. The amount ofhydrogen in the combined feedstock of olefins (butenes and ethylene) isadvantageously in the range of 0.1 to 10 vol % and preferably 0.2 to 5vol %.

The metathesis reaction can be carried out in liquid phase, gas phase,and mixed gas-liquid phase, which is determined by the reactiontemperature and pressure. Rhenium based catalyst performs preferablybetween 0 and 150° C. at a pressure to keep the feedstock in the liquidstate. Molybdenum based catalyst perform preferably at 100 to 250° C. inthe gas phase at from 1 to 30 bars pressure. Tungsten based catalystsperform preferably at 150 to 400° C. at a pressure of from 5 to 35 bars.The metathesis may be performed continuously in a fixed bed reactorconfiguration using a pair of parallel “swing” reactors, provided thecatalyst exhibits sufficient stability of at least 2 days. This enablesthe methathesis process to be performed continuously in two parallel“swing” reactors wherein when one reactor is operating; the otherreactor is undergoing catalyst regeneration. When the catalyst stabilityis shorter than about 2 days, metathesis may also be performedcontinuously in a moving bed reactor in which the catalyst circulatesfrom a reaction zone to a regeneration zone and backwards with aresidence time of the catalyst in the reaction zone of at least 5 hours.In each zone the catalyst behaves substantially like in a fixed bedreactor, but the catalyst moves slowly, by gravity or pneumaticallythrough the respective zone. The use of a moving bed reaction allowsaccomplishing a continuous operation with no switching of the feedstockand regeneration gas from one reactor to another one. The reaction zonereceives continuously the feedstock while the regeneration zone receivescontinuously the regeneration gas.

The metathesis can be done with only a mixture of n-butenes and iscommonly known as autometathesis. The products are propylene andpentenes. The propylene desired product is recovered while the pentenescan be recycled back to the metathesis reaction section. The metathesiscan also been carried out by adding ethylene to the n-butenes feedstock,commonly known as co-metathesis. The molar ratio of ethylene ton-butenes is advantageously from 0.75 to 5, preferably from 1 to 2.5.

As regards the products of the metathesis reaction, the reactor effluentcontains non-converted ethylene, if any was added to the reactionsection, and butenes, some heavies and the desired propylene product. Ina de-ethaniser the ethylene, eventually hydrogen when used, is producedoverhead and recycled back to the metathesis reactor. The bottom productis further separated in a de-propaniser where the overhead product isthe desired propylene. The bottom product is typically butenes and someheavier olefins. The butenes can be recycled back to the metathesisreactor for further reaction.

EXAMPLES Experimental

The stainless-steel reactor tube has an internal diameter of 10 mm. 10ml of catalyst, as pellets of 35-45 mesh, is loaded in the tubularreactor. The void spaces before and after the catalyst are filled withSiC granulates of 2 mm. The temperature profile is monitored with theaid of a thermocouple well placed inside the reactor. The reactortemperature is increased at a rate of 60° C./h to 550° C. under air,kept 2 hours at 550° C. and then purged by nitrogen. The nitrogen isthen replaced by the feed at the indicated operating conditions. Thecatalytic tests are performed down-flow, with a pressure of about 1.5bara, with a temperature of about 575° C. and with a weight hour spacevelocity (WHSV) of about 7 h⁻¹.

Analysis of the products is performed by using an on-line gaschromatography.

Example 1

The catalyst is a phosphorous modified zeolite (P-ZSM5), preparedaccording to the following recipe. A sample of zeolite ZSM-5 (Si/Al=13)in H-form was steamed at 550° C. for 6 h in 100% H₂O. Then, 600 g of thesteamed solid was subjected to a contact with 114 g of an aqueoussolution of H₃PO₄ (85% wt) for 2 h under reflux condition (4 ml/1 gzeolite) followed by addition of 34 g of CaCO3. Then the solution wasdried by evaporation under rigours stirring for 3 days at 80° C. 685 gof the dried sample was extruded with 401.5 g of silica sol Bindzil (34wt % SiO2), and 3 wt % of extrusion additives. The shaped samplecontained about 80 wt % zeolite. The extruded solid was dried at 110° C.for 16 h and steamed at 600° C. for 2 h.

For the following experiment, an isobutanol feed has been tested inmixture with water (ratio 95/5 wt %), under 1.5 bara, with a isobutanolspace velocity of 7 h-1 and a temperature of about 575° C. The table 1presents the average catalyst performance for 40 hours-on-stream. Theresults are given in the table 1 on CH2-basis and coke free basis. Thecatalyst has not presented signs of deactivation after about 90 hours inoperation.

Comparative Example

The test under the same condition on the same catalyst has been donewith ethanol/H2O blend. The table 1 presents the average catalystperformance for 40 hours-on-stream. The results are given in the table 1on CH2-basis and coke free basis.

TABLE 1 Example 1 95 wt % Comparative 95 wt % FEED i-Butanol/5 wt % H2OEthanol/5 wt % H2O P, bara 2 2 T, oC 575 575 WHSV, h-1 7.4 7.4Conversion, % 100 100 Selectivity on CH2 basis, % Ethylene 7.9 93Propylene 33.3 2.5

The conversions are complete in both cases, but the propyleneselectivity was only about 2.5% using ethanol as a feedstock and 33.3%using isobutanol. These examples illustrate that potentiallybio-propylene can be produced more efficiently from bio-i-butanol thanfrom bio-ethanol.

Example 2

The catalyst is a phosphorous modified zeolite (P-ZSM5), preparedaccording to the following recipe. A sample of zeolite ZSM-5 (Si/Al=13)in H-form was steamed at 550° C. for 6 h in 100% H₂O. Then, 1270 g ofthe steamed solid was subjected to a contact with 241.3 g of an aqueoussolution of H₃PO₄ (85% wt) for 2 h under reflux condition (4 ml/1 gzeolite) followed by addition of 69.9 g of CaCO3. Then the solution wasdried by evaporation under rigours stirring for 3 days at 80° C. 750 gof the dried sample was extruded with 401.5 g of silica sol Bindzil (34wt % SiO2) and 3 wt % of extrusion additives. The shaped samplecontained about 80 wt % zeolite. The extruded solid was dried at 110° C.for 16 h and steamed at 600° C. for 2 h.

For the following experiments, an isobutanol feed has been tested inmixture with water (ratio 95/5 wt %), under 1.5 bara, with a isobutanolspace velocity of 7 h-1 and a temperature of about 575° C.

The isobutanol conversion is complete and the major products arepropylene and C4 olefins. The C3=selectivity reaches about 36 wt % (onCH2 basis) and the C4=selectivity about 27 wt % (on CH2 basis).

The table 2 presents the average catalyst performance for 40hours-on-stream. The results are given in the table 1 on CH2-basis andcoke free basis. The catalyst has not presented signs of deactivationafter about 90 hours in operation.

TABLE 2 i-BuOH/H2O FEED 95/5% wt P (bara) 1.5 T (° C.) 575 WHSV (H-1)7.4 Conversion 100 HC Selectivity on CH2-basis Ethylene 10.6 Propylene36.3 C4 olefins 27.1

The invention claimed is:
 1. A process comprising: a) introducing in a reactor a stream comprising an alcohol mixture, optionally water, optionally an inert component, wherein the alcohol mixture comprises from 40 to 100 weight percent isobutanol based on a total weight of the alcohol mixture, b) contacting said stream with a single catalyst at a temperature above 450° C. in said reactor at conditions effective to dehydrate at least a part of the isobutanol and other alcohols, if any, forming C₄ ⁺ olefins, and to catalytically crack the C₄ ⁺ olefins, wherein the single catalyst is an acid catalyst adapted to cause both the dehydration and the catalytic cracking, c) recovering from said reactor an effluent comprising: ethylene, propylene, water, optionally unconverted alcohols of the alcohol mixture, various hydrocarbons, and the optional inert component of step a), d) fractionating said effluent of step c) to produce at least an ethylene stream, a propylene stream, a fraction comprising hydrocarbons having 4 carbon atoms or more, water and the optional inert component of step a), optionally recycling ethylene in whole or in part at an inlet of the reactor, optionally recycling the fraction comprising hydrocarbons having 4 carbon atoms or more at the inlet of the reactor; wherein the single catalyst comprises a dealuminated crystalline silicate containing at least one 10 member ring in the structure thereof.
 2. The process according to claim 1, wherein, before recycling said hydrocarbons having 4 carbon atoms or more at the inlet of the reactor, said hydrocarbons having 4 carbon atoms or more are sent to a second fractionator to purge the heavies comprising hydrocarbons having more than 4 carbon atoms, water and optionally oxygenates.
 3. The process according to claim 1, wherein the alcohol mixture is subjected to purification to reduce a content of metal ions in the alcohol mixture.
 4. The process of claim 3, wherein the metal ions are selected from Na, Fe, K, Ca and Al.
 5. The process according to claim 1, wherein the temperature in the reactor of step a) and b) is up to 650° C.
 6. The process according to claim 1, wherein the fraction comprising hydrocarbons having 4 carbon atoms or more recovered at step d) comprises 2-butene, and wherein the process further comprises reacting ethylene with the 2-butene from the fraction comprising hydrocarbons having 4 carbon atoms or more recovered at step d) to produce propylene.
 7. The process according to claim 1, further comprising recovering n-butenes from the fraction comprising hydrocarbons having 4 carbon atoms or more recovered at step d) and reacting the n-butenes in an automethathesis to produce propylene and pentenes.
 8. The process according to claim 1, further comprising fermenting carbohydrates coming from a biomass, or from a syngas route or from a base-catalysed Guerbet condensation to obtain the isobutanol.
 9. The process according to claim 1, further comprising producing the isobutanol by the direct 2-keto acid pathway from carbohydrates that are isolated from biomass.
 10. The process according to claim 1, wherein ethylene is further polymerized optionally with one or more comonomers.
 11. The process according to claim 1, wherein propylene is further polymerized optionally with one or more comonomers.
 12. The process according to claim 1, wherein the crystalline silicate is an MFI, MEL, FER, MTT, MWW, TON, EUO, MFS, CON or ZSM-48.
 13. The process according to claim 1, wherein the crystalline silicate is ZSM-5, silicalite-1, boralite C, TS-1, ZSM-11, silicalite-2, boralite D, TS-2, SSZ-46, Ferrierite, FU-9, ZSM-35, ZSM-23, MCM-22, PSH-2, ITQ-1, MCM-49, ZSM-22, Theta-1, NU 10, ZSM-50, EU-1, ZSM-57, CIT-1, or ZSM-48.
 14. The process according to claim 1, wherein the crystalline silicate has a Si/Al ratio of at least
 100. 15. The process of claim 14, wherein the crystalline silicate is an MFI or MEL and is modified with a metal and comprises a metal content of at least 0.1 weight percent based on a total weight of the crystalline silicate, and wherein the metal is selected from the group consisting of Mg, Ca, La, Ni, Ce, Zn, Co, Ag, Fe and Cu.
 16. The process of claim 1, wherein the crystalline silicate is mixed with a binder.
 17. The process of claim 16, wherein the binder is selected from clays, silica, metal silicate, metal borates, metal oxides, and gels including mixtures of silica and metal oxides.
 18. The process according to claim 1, wherein the crystalline silicate is silicalite-1, boralite C, TS-1, silicalite-2, boralite D, TS-2, SSZ-46, Ferrierite, FU-9, ZSM-35, ZSM-23, MCM-22, PSH-2, ITQ-1, MCM-49, ZSM-22, Theta-1, NU 10, ZSM-50, EU-1, ZSM-57, CIT-1, or ZSM-48.
 19. The process according to claim 1, wherein the crystalline silicate is silicalite-1, boralite C, TS-1, silicalite-2, boralite D, TS-2, SSZ-46, FU-9, ZSM-35, ZSM-23, MCM-22, PSH-2, ITQ-1, MCM-49, ZSM-22, Theta-1, NU 10, ZSM-50, EU-1, ZSM-57, CIT-1, or ZSM-48. 